1. Field of the Invention
The present invention relates to a front end circuit that is provided in a multiband communication device that communicates while handling a plurality of frequency bands, and is located between a communication circuit and an antenna therein.
2. Description of the Related Art
In a front end circuit handling transmission/reception signals of a plurality frequency bands, such a circuit converts a reception signal to a balanced signal and outputs the obtained balanced signal to a reception circuit, as disclosed in Japanese Unexamined Patent Application Publication No. 2006-237978, for example.
FIG. 4 is a circuit diagram of a multiband communication device disclosed in Japanese Unexamined Patent Application Publication No. 2006-237978. This example includes two antennas ANT1 and ANT2, a DPDT switch, a reception side circuit, and a transmission side circuit. The reception side circuit includes a reception side duplexer and two baluns 12 and 2.
By converting a reception signal to a balanced signal and outputting the obtained balanced signal to a low noise amplifier (LNA), a radio frequency integrated circuit (RFIC), or the like in the manner described above, noise immunity of the reception signal is improved.
In the multiband communication device as shown in FIG. 4, reception signals of different frequency bands, after having passed a reception side duplexer, experience balance-conversion performed by different baluns. In this manner, conventional multiband communication devices generally include baluns corresponding to the frequency bands. Accordingly, as the frequency bands increase in number, the number of baluns increases, which arrests miniaturization of the overall circuit.